Prevalence and size of pelvic sentinel lymph node metastases in endometrial cancer.

Aim Of The Study: To assess the association of prevalence and size of pelvic sentinel node (SLN) metastases with risk factors in endometrial cancer (EC).

Patients And Methods: Between June 2014 and January 2024 consecutive women with a uterine confined EC undergoing robotic surgery including detection of pelvic SLNs at a University Hospital were included. An anatomically based algorithm utilizing Indocyanine green (ICG) as tracer was adhered to. Ultrastaging and immunohistochemistry (IHC) was applied on all SLNs. The prevalence and size of SLN metastases was assessed with regards to pre- and postoperative histologic types and myometrial invasion estimates.

Results: Of 1101 included women 72.6 % (759/1045) had low-grade, 7.6 % (79/1045) high-grade endometroid cancer and 19.8 % (207/1045) non-endometroid cancer. SLN-metastases were present in 174/1045 (16.6 %) women; 9.8 % of preoperatively presumed low-grade endometroid uterine stage 1A (6.4 % of low-grade stage 1A at final histology) and in 58.3 % and 47.8 % respectively in women with high-grade endometroid and non-endometroid uterine stage 1B cancer. In low-grade EC 45/95 (47.4 %) had only isolated tumor cells (ITC) in SLNs compared with 15/78 (19.2 %) in high-grade or non-endometroid cancer (p < .0001) CONCLUSION: This large population-based study, applying a consequent SLN-algorithm over time, provides important detailed information on the risk for, and size of, SLN metastases within risk groups of EC. The 9.8 % risk for metastases in women with presumed low grade uterine stage 1A endometrioid EC motivates detection of SLNs within this subgroup. The proportion of ITCs in SLNs was significantly lower in higher risk histologies.